This disclosure of Japanese Patent Application No. 2002-014404 filed on Jan. 23, 2002 including the specification, drawings and abstract is incorporated herein by reference in the entirety.
1. Field of Invention
The invention relates to a control unit of an electromagnetically driven valve and a control method of the electromagnetically driven valve.
2. Description of Related Art
There is known a control unit of an electromagnetically driven valve for controlling opening and closing of a valve body of the electromagnetically driven valve serving as an intake valve or an exhaust valve of an internal combustion engine in response to energization and de-energization of an electromagnet. Generally the electromagnetically driven valve includes an electromagnet that generates electromagnetic force for attracting an armature which reciprocates together with the valve body, and a pair of springs for urging the valve body towards opposite ends of the valve-closing side and valve-opening side, that is, the fully-closed position and fully-opened position of the valve body, respectively. The respective spring forces of the pair of springs are set so as to be balanced with each other when the valve body is located in xe2x80x9ca neutral positionxe2x80x9d as a substantially middle position between the valve closing end and the valve opening end.
Japanese Laid-Open Patent Publication No. 2000-34912 discloses another type of the electromagnetically driven valve, which includes an air pressure spring in place of the ordinary spring as indicated above. The air pressure spring of the electromagnetically driven valve includes a cylinder, a piston disposed within the cylinder, and a pressure chamber defined by the cylinder and the piston. The air pressure spring is adapted to urge, via the piston, the valve body using the pressure of compressed air stored in the pressure chamber.
In the aforementioned internal combustion engine (hereinafter simply referred to as an xe2x80x9cenginexe2x80x9d where appropriate) including a control system that controls such electromagnetically operated valves serving as intake and exhaust valves, the number of open/close operations of one or more of the electronically valves may be reduced during a low load operation of the engine. In this case, the valve body of the intake valve or the exhaust valve, which is to be stopped may be held in a fully-opened position or a fully-closed position. The valve body is urged by a spring force of the spring so as to be returned to the neutral position. Therefore, the valve body is held in the fully-opened or the fully-closed position against the spring force of the spring in the stopped state of the open and close operation of the valve using the electromagnetic force generated by applying holding current to the electromagnet. Accordingly, this may hinder reduction in power consumption of the control unit of the electromagnetically driven valve.
It is therefore an object of the invention to provide a control unit of an electromagnetically driven valve, which save energy for holding the valve body of the electromagnetically driven valve in the fully-opened or fully-closed position in the stopped state of the open and close operation of the electromagnetically driven valve.
Hereinafter, the structure of the control unit of the electromagnetically driven valve of the invention, effects and advantages thereof will be described hereinafter.
In an embodiment of the invention, a control unit of an electromagnetically driven valve is provided. The electromagnetically driven valve includes a valve body, an electromagnetic drive portion and a spring so as to be opened and closed by an electromagnetic force of the electromagnetic drive portion and a spring force of the spring that is formed of a pair of gas pressure springs each urging the valve body towards a valve opening end position and a valve closing end position, respectively. The control unit includes a controller, when an operation of the valve body is stopped and held in a holding position that is one of the valve opening end position and the valve closing end position, decreases a gas pressure of one of the pair of gas pressure springs that urges the valve body towards a non-holding position opposite to the holding position so as to become lower than a gas pressure of the one of the pair of gas pressure springs that urges the valve body towards the non-holding position when the valve body is operated.
According to the embodiment of the invention, when the valve body is held in a holding position as one of the fully-opened and the fully-closed position in the stopped state of the open and close operation of the valve, the gas pressure of the spring that urges the valve body towards the non-holding position as the other one of the fully-opened and the fully-closed position is decreased to be lower than the gas pressure of the spring during the open and close operation of the valve. More specifically, when the valve body is held in the fully-opened position, the gas pressure of the gas spring that urges the valve body towards the fully-closed position is decreased. Meanwhile, when the valve body is held in the fully-closed position, the gas pressure of the gas spring that urges the valve body towards the fully-opened position is decreased.
Accordingly, the spring force that moves the valve body away from the holding position may be reduced. This makes it possible to reduce the electromagnetic force of the electromagnet required for holding the valve body in the holding position, thus reducing the holding current.
When the gas pressure of the gas spring that urges the valve body towards the non-holding position is reduced to be lower than a predetermined value, a resultant force of the springs may be directed towards the holding position. This makes it possible to hold the valve body in position without applying the holding current to the electromagnet.
The aforementioned structure may allow reduction of energy required for holding the valve body in the holding position that is either the fully-opened position or the fully-closed position in a stopped state of open and close operation of the electromagnetically driven valve.
In the embodiment, the controller controls a gas pressure of a pressure chamber of one of the pair of gas pressure springs such that a spring force of the one of the pair of gas pressure springs that urges the valve body towards the non-holding position becomes smaller than a spring force of the other gas pressure spring that urges the valve body towards the holding position when the operation of the valve body is stopped and held in the holding position.
According to the embodiment, when the valve body is held in the holding position in its stopped state, the gas pressure of the gas pressure spring is controlled. More specifically, in the state where the valve body is held in the holding position, the gas pressure is controlled such that the spring force of the spring for urging the valve body towards the non-holding end is reduced to be smaller than that of the gas pressure spring for urging the valve body towards the holding position. That is, the resultant force of the gas pressure springs in the holding position may be directed towards the holding position.
Such control of the gas pressure may be executed by reducing the gas pressure within the pressure chamber of the gas pressure spring for urging the valve body towards the non-holding end, increasing the gas pressure within the pressure chamber of the gas pressure spring for urging the valve body towards the holding end, or combination thereof.
The aforementioned structure makes it possible to hold the valve body in the holding position without requiring the electromagnetic force of the electromagnet. As a result, the energy required for holding the valve body in the holding position either the fully-opened position or the fully-closed position in the stopped state of the open and close operation of the electromagnetically driven valve.